Greater Stiffness Research Articles

Investigating the effect of autograft diameter for quadriceps and patellar tendons use in anterior cruciate ligament reconstruction: a biomechanical analysis using a simulated Lachman test.

Current clinical practice suggests using patellar and quadriceps tendon autografts with a 10 mm diameter for ACL reconstruction. This can be problematic for patients with smaller body frames. Our study objective was to determine the minimum diameter required for these grafts. We hypothesize that given the strength and stiffness of these respective tissues, they can withstand a significant decrease in diameter before demonstrating mechanical strength unviable for recreating the knee's stability. We created a finite element model of the human knee with boundary conditions characteristic of the Lachman test, a passive accessory movement test of the knee performed to identify the integrity of the anterior cruciate ligament (ACL). The Mechanical properties of the model's grafts were directly obtained from cadaveric testing and the literature. Our model estimated the forces required to displace the tibia from the femur with varying graft diameters. The 7 mm diameter patellar and quadriceps tendon grafts could withstand 55-60 N of force before induced tibial displacement. However, grafts of 5.34- and 3.76-mm diameters could only withstand upwards of 47 N and 40 N, respectively. Additionally, at a graft diameter of 3.76 mm, the patellar tendon experienced 234% greater stiffness than the quadriceps tendon, with similar excesses of stiffness demonstrated for the 5.34- and 7-mm diameter grafts. The patellar tendon provided a stronger graft for knee reconstruction at all diameter sizes. Additionally, it experienced higher maximum stress, meaning it dissociates force better across the graft than the quadriceps tendon. Significantly lower amounts of force were required to displace the tibia for the patellar and quadriceps tendon grafts at 3.76- and 5.34-mm graft diameters. Based on this point, we conclude that grafts below the 7 mm diameter have a higher chance of failure regardless of graft selection.

Improving the behavior of concentrically braced frame braces using a flexural damper: Experimental and numerical study

SummaryAlthough the concentrically braced frames (CBFs) systems have high lateral elastic stiffness and strength, they reflect a low seismic energy absorption capacity mainly due to their diagonal buckling under compressive loading. To overcome this problem, researchers have proposed metallic shear damper as the most popular due to its satisfactory performance and affordable cost. In this paper, an innovative metallic damper with a flexural mechanism is proposed to improve the behavior of CBF systems. It provides ease of fabrication and replacement after damage, competitive cost, and improved resistance to buckling of the CBF member. The performance of the damper was evaluated experimentally and numerically. Subsequently, two types of dampers, (a) made of rectangular flexural plates (RFP) and (b) made of I‐shaped flexural plates (IFP), were designed and evaluated. Experimental as well as numerical results indicated that both dampers provide stable and symmetrical hysteresis curves with a high energy absorption capacity. Results indicated that the IFP damper has greater stiffness (1.94–2.3 times) and ultimate strength (1.76 times) but a lower overstrength (66% less) and ductility (47% less) than the RFP damper. Moreover, design expressions were presented for the proposed damper and showed a good agreement with finite element results.

Impact of Quadriceps Tendon Graft Thickness on Electromechanical Delay and Neuromuscular Performance After ACL Reconstruction.

Both partial- and full-thickness quadriceps tendon (QT) graft harvests are used for anterior cruciate ligament reconstruction (ACLR). To evaluate the impact of QT graft harvest depth (full or partial thickness) on electromechanical delay (EMD), peak torque (PT), and rate of torque development (RTD) after ACLR. Controlled laboratory study. A total of 26 patients who underwent either partial-thickness (n = 14) or full-thickness (n = 12) autograft QT ACLR were recruited between June and November 2021 (>1 year before participation). Patients performed isokinetic knee extension testing with surface electromyography of the quadriceps muscles. Mixed repeated-measures analysis of variance with least significant difference post hoc testing was used to determine significant differences (mean difference [MD] ± SE) or interactions for all variables. A significant speed×depth interaction was seen for the vastus medialis (P = .005). Pairwise analyses showed significantly longer EMD for the partial-thickness graft than the full-thickness graft (MD ± SE, 19.92 ± 6.33 ms; P = .006). In the partial-thickness graft, the EMD was significantly longer at 90 deg/s versus 180 deg/s (MD ± SE, 19.11 ± 3.95 ms; P < .001) and 300 deg/s (MD ± SE, 16.43 ± 5.30 ms; P = .006). For PT, the full-thickness graft had a significantly lower PT on the operated versus nonoperated side at all speeds (MD ± SE: 90 deg/s, -57.0 ± 10.5 N·m, P < .001; 180 deg/s, -26.0 ± 10.2 N·m, P = .020; 300 deg/s, -20.3 ± 8.9 N·m, P = .034). For RTD, the full-thickness graft showed significantly Slower RTD for the operated versus nonoperated side at all time points (MD ± SD: RTD0-25 (0-25% of the range of motion), -131.3 ± 50.9 N·m/s, P = .018; RTD25-50, -197.0 ± 72.5 N·m/s, P = .014; RTD50-75, -113.3 ± 39.8 N·m/s, P = .013; RTD75-100, -149.4 ± 35.9 N·m/s, P < .001). Compared with partial-thickness QT, full-thickness QT showed a shorter vastus medialis EMD at higher loading, and therefore greater stiffness, as well as slower RTD and lower PT across all testing speeds. The impact of full-thickness QT autograft on EMD and neuromuscular performance should be considered for ACLR.

Research on mechanical property of glued timber truss connected by steel plates and bolts

In order to deeply understand the mechanical performance of glued-laminated timber trusses connected by steel-plates and bolts, two groups of truss specimens were designed and fabricated by changing the connection forms of the nodes, while maintaining the height and span of the trusses unchanged. Each group of truss specimens was subjected to the mid-span load. At the same time, finite element numerical analysis was conducted on the tested trusses. Based on the agreement between the experimental and numerical simulation results, the influence of the parameters of thickness-to-diameter ratio and height-to-span ratio on the mechanical performance of these trusses was explored. The research results show that both types of node connections in the glued-laminated timber trusses have good bearing capacity. The main failure modes are the splitting of the diagonal web members at the mid-span node and the crushing failure of the bolt holes. The HJ-C type truss, which has the upper and lower chord members connected, exhibits better ductility, greater stiffness, and better structural synergy in load-bearing capacity. As the thickness-to-diameter ratio increases, the form of the bolts at the truss failure gradually changes from being straight to yielding. The optimal thickness-to-diameter ratio is 8.3. As the height-to-span ratio decreases, the initial stiffness and ultimate load-bearing capacity of the truss show a decreasing trend. The truss exhibits better mechanical performance when the height-to-span ratio is 1/4.

Evaluation of impact response of thermal-damaged FRP-RC slabs: Effects of FRP bar type and concrete cover thickness

The purpose of present study is to investigate the impact response of FRP-RC slabs under elevated temperatures. Considering the high-temperature degradation effect and strain rate enhancement effect of FRP bars and concrete materials, a numerical model for studying the fire and impact resistance of FRP-RC slabs was established and verified. The impact failure mechanism of in-fire thermal-damaged FRP-RC slabs was analyzed. The influence of the type of FRP bars, concrete cover thickness and fire duration on the in-fire impact resistance of FRP-RC slabs was revealed. Ultimately, the post-fire residual bearing capacity of the slabs after elevated temperature and impact was obtained. The results show that the typical local punching failure mode is not affected by thermal damage while energy dissipated by concrete accounts for most of the impact energy absorbed by the slabs. When exposed to fire for 60 min, the elevated temperature significantly deteriorates the impact resistance of FRP-RC slabs with a cover thickness of 15 mm. At this time, the greater the concrete cover thickness, the better the impact resistance of FRP-RC slabs. Under the combined action of elevated temperature and impact, Carbon FRP-RC slabs have greater stiffness, lower deflection, greater impact plateau value, less impact duration and lower energy consumption than Aramid FRP, Basalt FRP and Glass FRP-RC slabs. Moreover, the damage index of the slab based on residual bearing capacity and peak displacement is approximately linearly positively correlated. The influence of the concrete cover thickness is more prominent on the damage index based on the peak displacement.

Antegrade Fixation of Distal Metaphyseal Ulnar Shortening Osteotomy.

The ulnar shortening osteotomy (USO) is a common procedure used to treat ulnar impaction syndrome secondary to static or dynamic ulnar-positive variance. There are many described techniques for the USO. The distal metaphyseal ulnar shortening osteotomy (DMUSO) with retrograde cannulated screw fixation was described to reduce complications seen with other techniques. Biomechanical analysis of fixation constructs demonstrates 2-screw constructs are significantly stiffer than 1 screw and antegrade constructs have similar or greater stiffness when compared with retrograde constructs. Here, we describe a technique of antegrade cannulated screw fixation for DMUSO that obviates the need for the disruption of the distal radioulnar joint for intra-articular exposure of the ulnar head. Similar to the traditional retrograde DMUSO technique, this construct may also decrease the risk of delayed union, symptomatic implants associated with diaphyseal osteotomies, and disruption of triangular fibrocartilaginous complex in wafer procedures.

Racial and Ethnic Disparities in Pediatric Musculoskeletal Care.

This article provides a review of recent published research studying racial, ethnic, and socioeconomic disparities in pediatric musculoskeletal care. Disparities in pediatric musculoskeletal care are demonstrated in two general realms: access to care and health outcomes. Though initiatives have been proposed or enacted to address disparities, underrepresented minorities and patients from lower socioeconomic statuses continue to face barriers across the spectrum of orthopedic care and poorer ultimate outcomes after both non-operative and operative management. Minority pediatric patients and those from lower socioeconomic statuses experience delays across the spectrum of orthopedic care for both urgent and non-urgent conditions. They wait longer between injury date and initial orthopedic evaluation, longer to receipt of diagnostic imaging, and longer to ultimate treatment than their counterparts. When finally able to obtain musculoskeletal care and treatment, they are at higher risk of poor in-hospital outcomes and inpatient complications, worse patient reported outcomes, and suboptimal pain management. In the outpatient setting, they receive less physical therapy and follow-up clinic visits, resulting in greater stiffness and strength deficits, and are ultimately less likely to meet return to sport criteria.

Age-Related Changes of the Zygomatic Ligament: An Experimental Animal Study.

Facial aging is a multifactorial process involving the skin, fat, muscles, bones, and ligaments. The role of facial ligaments in the facial aging process remains elusive. The aim of this study was to identify whether age-related changes in facial ligaments exist and how to best quantify such changes when investigating the zygomatic ligament in the rat. A total of 30 male Sprague-Dawley rats (10 young, 10 middle-aged, 10 mature) were investigated to visualize the zygomatic ligament. Samples of the ligaments spanning the zygomatic arch and the skin were taken and histologically examined with hematoxylin-eosin, Masson, Verhoeff's elastic, and picrosirius red staining. Quantification of the Type I/III collagen ratio and collagen content was performed by color deconvolution and electron microscopic imaging. With increasing age, collagen fibers inside of the examined ligaments appeared thicker and more closely arranged. The Type I/III collagen ratio was measured to be 1.74 in young animals, 3.93 in middle-aged animals, and 5.58 in mature animals. The ultra-microstructure of the ligament was less coordinated in direction and orientation in young and middle-aged animals than in mature animals, in which collagen fibers were bundled together in a strong and oriented mesh. Ligaments appeared thinner, transparent, more elastic, and less robust in young animals, whereas ligaments in mature animals appeared thicker, more fascia-like, less elastic, and more robust. An increase in the Type I/III collagen ratio, indicating greater stiffness and reduced elasticity, was observed with higher age of the investigated animals. These findings indicate that ligaments might increase in stiffness and rigidity with age.

Tape-Reinforced Graft Suturing and Retensioning of Adjustable-Loop Cortical Buttons Improve Quadriceps Tendon Autograft Biomechanics in Anterior Cruciate Ligament Reconstruction: A Cadaveric Study

To investigate the biomechanical effects of tape-reinforced graft suturing and graft retensioning for all-soft tissue quadriceps tendon (ASTQT) anterior cruciate ligament reconstruction (ACLR) in a full-construct human cadaveric model. Harvested cadaveric ASTQT grafts were assigned to either (1) double-suspensory adjustable-loop cortical button device (ALD) fixation in which both graft ends were fixed with a suspensory fixation device with (n= 5) or without (n= 5) tape-reinforced suturing or (2) single-suspensory distal tendon fixation in which only the patellar end was fixed with an ALD (n= 5) or fixed-loop cortical button device (FLD) (n= 5). All specimens were prepared using a No. 2 whipstitch technique, and tape-reinforced specimens had an integrated braided tape implant. Graft preparation time was recorded for double-suspensory constructs. Samples were tested on an electromechanical testing machine using a previously published protocol simulating rehabilitative kinematics and loading. Tape-reinforced graft suturing resulted in greater graft load retention after cycling (11.9% difference, P= .021), less total elongation (mean [95% confidence interval (CI)], 5.57 mm [3.50-7.65 mm] vs 32.14 mm [25.38-38.90 mm]; P < .001), greater ultimate failure stiffness (mean [95% CI], 171.9 N/mm [158.8-185.0 N/mm] vs 119.4 N/mm [108.7-130.0 N/mm]; P < .001), and less graft preparation time (36.4% difference, P < .001) when compared with unreinforced specimens. Retensioned ALD constructs had less cyclic elongation compared with FLD constructs (mean total elongation [95% CI], 7.04 mm [5.47-8.61 mm] vs 12.96 mm [8.67-17.26 mm]; P= .004). Tape-reinforced graft suturing improves time-zero ASTQT ACLR construct biomechanics in a cadaveric model with 83% less total elongation, 44% greater stiffness, and reduced preparation time compared with a whipstitched graft without tape reinforcement. ALD fixation improves construct mechanics when compared with FLD fixation as evidenced by 46% less total elongation. Tape-reinforced implants and graft retensioning using ALDs improve time-zero ACLR graft construct biomechanics in a time-zero biomechanical model. Clinical studies will be necessary to determine whether these implants improve clinical outcomes including knee laxity and the incidence of graft rupture.

Ultimate behaviour of hybrid stainless steel cross-sections

Hybrid steel plate girders are used worldwide as primary structural members in steel and composite bridges, when there is a need for deeper sections with greater stiffness and bending resistance than rolled sections to carry heavy loads. With the increasing importance of sustainability and lifecycle (cost) analysis, design for maintenance has become an important consideration for infrastructure projects like bridges which have a design working life exceeding 100 years over which they need to be regularly inspected and maintained. Stainless steels are known for their excellent corrosion resistance and low maintenance costs and thus the application of hybrid plate girders in bridge designs could be explored. This paper reports a numerical study on stainless steel hybrid plate girders subjected to compression and to bending and assesses relevant recommendations for their design. Previously developed FE models validated against stub column and four-point bending tests are employed and a parametric study is conducted on hybrid I-sections over a wide range of cross-section slenderness and aspect ratios. Based on the obtained results, the EN 1993-1-4 design predictions for stainless steel cross-sections in compression and in bending are assessed and the accuracy of the codified slenderness limits for both homogeneous and hybrid stainless steel girders is discussed. Furthermore, the numerically obtained deformation capacity at ultimate load is plotted against the CSM base curve originally derived for homogeneous sections and the accuracy of the CSM predictions of the cross-section resistance is also assessed, demonstrating that the CSM can be employed to predict the cross-section resistance of hybrid girders.

Biophysical Properties of the Fibril Structure of the Toxic Conformer of Amyloid-β42: Characterization by Atomic Force Microscopy in Liquid and Molecular Docking.

Alzheimer's disease is associated with the aggregation of the misfolded neuronal peptide, amyloid-β42 (Aβ42). Evidence has suggested that several reasons are responsible for the toxicity caused by the aggregation of Aβ42, including the conformational restriction of Aβ42. In this study, one of the toxic conformers of Aβ42, which contains a Glu-to-Pro substitution (E22P-Aβ42), was explored using atomic force microscopy and molecular docking to study the aggregation dynamics. We proposed a systematic model of fibril formation to better understand the molecular basis of conformational transitions in the Aβ42 species. Our results demonstrated the formation of amorphous aggregates in E22P-Aβ42 that are stem-based, network-like structures, while the formation of mature fibrils occurred in the less toxic conformer of Aβ42, E22-Aβ42, that are sphere-like flexible structures. A comparison was made between the biophysical properties of E22P-Aβ42 and E22-Aβ42 that revealed that E22P-Aβ42 had greater stiffness, dihedral angle, number of β sheets involved, and elasticity, compared with E22-Aβ42. These findings will have considerable implications toward our understanding of the structural basis of the toxicity caused by conformational diversity in Aβ42 species.

Structural performance of rigid shear connectors in concrete encased steel composite columns

Concrete encased steel (CES) composite columns possess a wide variety of advantages in constructing concrete-steel composite frames. In order to achieve the composite behaviour of these columns, it is necessary to transfer the force between steel and concrete, effectively. Therefore, shear connectors should be used on the contact surface between concrete and steel. In this research, behaviour of the rigid shear connectors in CES composite columns is numerically studied. The results – obtained from the finite element analysis – were validated against the experimental results. Afterwards, parametric studies were conducted to investigate the effective parameters on the behaviour of the rigid shear connectors. The results show that the length, the thickness and the penetration depth of the shear connector, the compressive strength of concrete and the thickness of concrete cover have a noticeable effect on the strength and stiffness of the shear connector. Moreover, increasing the length and the penetration depth of the shear connector, and the thickness of the concrete would increase the residual strength level. In general, the rigid shear connector is mobilized under a much smaller slippage (between concrete and steel), as compared to the stud shear connector, and provides greater stiffness and strength. Moreover, due to being encased in reinforced concrete, it can also provide sufficient ductility. Finally, based on the parametric studies, a formula is suggested to predict the ultimate shear capacity of the rigid shear connector in the CES composite columns.

Application And Improvement of Composite Materials in Truss Bridge Structure

Composite materials are new materials with the features of light weight, high strength, high specific modulus, strong corrosion resistance, and aging resistance. The truss structure is subject to unidirectional force, which gives full play to the advantages of high strength of composite materials along the fiber direction. Therefore, composite truss structure is gradually attracted attention in engineering fields, i.e., aerospace, bridges, and construction. By analyzing the application status of composite truss bridge at home and abroad, it can be concluded that compared with traditional steel truss, composite truss bridge has advantages in flexural performance, tensile performance, stability and other mechanical properties. However, due to the stiffness control design, the strength of composite material is not fully utilized, and the structural reliability of composite truss bridge is low due to the low efficiency of structural joints. The improvement methods of these two problems are reducing the allowable deflection-span ratio of composite truss bridge design and using composite materials with greater stiffness and changing the laying Angle and laying proportion of composite materials, respectively.

Influence of internal muscle properties on muscle shape change and gearing in the human gastrocnemii.

Skeletal muscles bulge when they contract. These three-dimensional shape changes, coupled with fiber rotation, influence a muscle's mechanical performance by uncoupling fiber velocity from muscle belly velocity (i.e., gearing). Muscle shape change and gearing are likely mediated by the interaction between internal muscle properties and contractile forces. Muscles with greater stiffness and intermuscular fat, due to aging or disuse, may limit a muscle's ability to bulge in width, subsequently causing higher gearing. The aim of this study was to determine the influence of internal muscle properties on shape change, fiber rotation, and gearing in the medial (MG) and lateral gastrocnemii (LG) during isometric plantar flexion contractions. Multimodal imaging techniques were used to measure muscle shear modulus, intramuscular fat, and fat-corrected physiological cross-sectional area (PCSA) at rest, as well as synchronous muscle architecture changes during submaximal and maximal contractions in the MG and LG of 20 young (24 ± 3 yr) and 13 older (70 ± 4 yr) participants. Fat-corrected PCSA was positively associated with fiber rotation, gearing, and changes in thickness during submaximal contractions, but it was negatively associated with changes in thickness at maximal contractions. Muscle stiffness and intramuscular fat were related to muscle bulging and reduced fiber rotation, respectively, but only at high forces. Furthermore, the MG and LG had varied internal muscle properties, which may relate to the differing shape changes, fiber rotations, and gearing behaviors observed at each contraction level. These results indicate that internal muscle properties may play an important role in mediating in vivo muscle shape change and gearing, especially during high-force contractions.NEW & NOTEWORTHY Here, we measured internal muscle properties in vivo to determine their influence on the varying shape change and gearing behaviors in the synergistic gastrocnemii muscles. These relationships have previously only been hypothesized or examined within isolated muscles during supramaximal contractions. Our results contribute to a more comprehensive understanding of the factors that influence a muscle's mechanical response to force with implications for preventing or treating muscle deficits associated with aging, disease, and disuse.

In Situ Synchrotron HEXRD Study on the Deformation Mechanism of a Nickel-Based Superalloy during Medium-Temperature Compression

The γ′ phase has an important influence on the deformation mechanism of solid-solution strengthening nickel-based superalloys. The microfracture behavior of the alloy depends on the mechanism of stress and strain partitioning between the γ and γ′ phase under load. In this study, the in situ synchrotron radiation high-energy X-ray diffraction technique was used to observe the deformation process of the FGH96 nickel-based superalloy with a γ′ volume fraction of about 40% at 650 °C and 750 °C. The results show that the (111) reflection had the greatest stiffness and showed plastic deformation first; while the (200) reflection bore a larger load. The γ phase yielded first and began to deform plastically; then the load was transferred to the γ′ phase. At 650 °C, the plastic deformation of the γ′ phase was relatively higher; while at 750 °C, the γ′ particle basically maintained elastic deformation with a tiny amount of plastic deformation.

Structure and physical properties of predicted MAX phase V2SiC under pressure: A first principle calculation

MAX-phase materials are important for technical applications in different fields, where pressure can change the microstructure and thus the properties of the material. In this paper, the structural, electronic, mechanical, thermodynamic, and optical properties of the new ternary layered ceramic MAX phase V2SiC are investigated under different pressures based on DFT simulations. A greater stiffness along the c-axis than along the a-axis direction and a negative enthalpy of formation confirm the thermodynamic stability of the pressurized phase. Although the band structure is altered under pressure, the metallic properties are retained. The coexistence of its covalent, metallic, and ionic bonds is observed in the charge density diagram. The elastic constants satisfy the Born stability criterion, ensuring mechanical stability under pressurized and unpressurized conditions. The increase in υ from 0.239 to 0.279 indicates that the compound changes from brittle to ductile, with the maximum ductility observed at 20 GPa. Phonon calculations show its kinetic stability, and Helmholtz free energy, enthalpy, entropic specific heat capacity, and Debye temperature are also calculated. Optical properties show that V2SiC is suitable for optoelectronic devices in the visible and UV regions and also as a coating material to reduce the heat from sunlight at high pressures up to 10 GPa. This is the first comprehensive theoretical study of the properties of V2SiC and may provide a reference for future research, the results of which still require subsequent experimental verification.

Modeling the Impact of Meniscal Tears on von Mises Stress of Knee Cartilage Tissue.

The present study aims to explore the stressed state of cartilage using various meniscal tear models. To perform this research, the anatomical model of the knee joint was developed and the nonlinear mechanical properties of the cartilage and meniscus were verified. The stress-strain curve of the meniscus was obtained by testing fresh tissue specimens of the human meniscus using a compression machine. The results showed that the more deteriorated meniscus had greater stiffness, but its integrity had the greatest impact on the growth of cartilage stresses. To confirm this, cases of radial, longitudinal, and complex tears were examined. The methodology and results of the study can assist in medical diagnostics for meniscus treatment and replacement.

Comparative Investigations on Properties of Three Kinds of FDM 3D-Printed Natural Plant Powder/Poly(lactic acid) Biocomposites.

In order to further explore the feasibility of the application of the residue of Chinese herbal medicine in FDM 3D technology and enrich the kinds of printing materials, Astragalus residue powder(ARP)/poly(lactic acid) (PLA) biocomposite was FDM 3D-printed, meanwhile, two traditional biocomposites, i.e., wood flour (WF)/PLA and rice straw powder (RSP)/PLA, were prepared by the same method, and the properties of the biocomposites were comparatively investigated. The results showed that, the tensile and flexural strengths of ARP/PLA were 28.33 MPa and 97.60 MPa, respectively, which were 2.85% and 10.89% smaller than those of WF/PLA, while 15.73% and 7.04% greater than those of RSP/PLA. WF/PLA showed typical brittle fracture characteristics, ARP/PLA and RSP/PLA both showed ductile fracture, but not obviously. Among the three kinds of biocomposites, ARP/PLA was the most thermally stable, followed by WF/PLA and RSP/PLA in turn. The incorporation of natural plant powder had no significant effect on the glassy transition, melting, and cold-crystallization behaviors of PLA, but the crystallinity of PLA could be increased from 0.3% to 2.0% and 1.9%, respectively, by adding ARP and WF. At 20 °C, the storage modulus of ARP/PLA, WF/PLA and RSP/PLA was 2759.4 MPa, 3361.3 MPa, and 2691.5 MPa, respectively, indicating that WF/PLA has the greatest stiffness, and the stiffness of RSP/PLA was the least. In addition to these, all the biocomposites were hydrophilic, the contact angle of the distilled water on the surface of ARP/PLA, WF/PLA or RSP/PLA was correspondingly 73.5°, 77.6° and 71.2°. Overall, it can be concluded that ARP/PLA has moderate strengths, stiffness and wettability, meanwhile, it is the most thermal stable among the three biocomposites, and can be processed at a temperature close to that of PLA. ARP/PLA is suitable as a new kind of feedstock material for FDM 3D printing.

Untargeted metabolomics reveals the effect of rearing systems on bone quality parameters in chickens.

The objective of this study was to investigate the effects of rearing systems on the bone quality parameters in chickens using a metabolomics strategy. A total of 419 male one-day-old chicks were randomly allocated to two groups, a floor rearing group (FRG, n = 173) and a cage rearing group (CRG, n = 246). At 6, 8, 10, and 12weeks of age, all chickens were radiographed by a digital X-ray machine, and body weight was recorded. At 12weeks of age, 12 birds were selected from each group to obtain tibia and femur, and bone quality parameters of bone mineral density (BMD), mineral content (BMC), breaking strength (BBS), stiffness, Young's modulus (YM), ash content, calcium content, and phosphorus content were determined. An untargeted metabolomics assay was performed to identify changes in the serum metabolic profile (n = 8 birds/group). The results showed that cage-reared chickens had wider tibiae and greater body weight compared with floor-reared chickens. There were no significant differences in BMC or BBS between the two groups (p > 0.05), but BMD, ash content, calcium content, and phosphorus content of the tibia and femur of FRG were significantly higher than those of CRG (p < 0.05). Greater stiffness and YM of the femur were also observed in birds raised in the FRG compared with those raised in the CRG (p < 0.05). Taken together, the results suggest that rearing systems affected bone quality parameters. Furthermore, 148 and 149 differential metabolites were identified in positive and negative ion modes by LC-MS/MS analysis, among which 257 metabolites were significantly correlated with 16 bone quality parameters, including leucine, myristoleic acid, glycocholic acid, and N-phenylacetamide. KEGG analysis indicated that 15 metabolic pathways, including six pathways of amino acid metabolism, two pathways of lipid metabolism, and two pathways of carbohydrate metabolism, were responsible for bone quality. Overall, the present study demonstrated the effect of rearing systems on bone quality parameters, and identified several metabolites and metabolic pathways associated with bone quality parameters.

The effects of mechanical degradation on the quasi static and dynamic stiffness of polyester yarns

Polyester fibers are the most used in the manufacture of ropes for mooring systems and offshore operation, thus being constantly subjected to different situations. Such requests are implicated in a variety of load conditions, and their effects must be studied. This work presents data referring to an experimental study on the behavior of the quasi-static and dynamic stiffness of polyester yarns considering different mechanical levels of degradation and use. The study is performed with five different types of multifilament samples, these were extracted from a virgin spool and sub-ropes tested for tension and fatigue. The experimental procedure is carried out through an initial characterization where the linear density, the Yarn Break Load - YBL and the linear tenacity of the samples are determined. Continuing with the experimental tests, a procedure standardized by ISO 18962-2 is then carried out, consisting of three quasi-static stages and three dynamic stages, where the data acquired in the tests allow the determination of a dimensionless stiffness value. The results showed an increase in the quasi-static stiffness, tending to a plateau, and a linear increase in the dynamic stiffness, but with somewhat similar behavior between the samples. The results related to the total quasi-static stiffness also show that the specimens extracted from sub-ropes that underwent fatigue present greater total non-dimensionalized stiffness, this is indicative of the mechanical fatigue procedure as an improvement of the specimens, giving them greater stiffness, and consequently greater stresses rupture, a behavior that should be explored in future studies.